MORGULIS. — DEVELOPMENT OF TOXOPNEUSTES VARIEGATUS. 143 



Experiments with Digitalin and Quinine. 



As in the previously described experiments, five tenths per cent 

 aqueous solutions of digitalin and of quinine sulphate have been used 

 as standard solutions, and of these, various quantities of each were 

 added to the sea-water. Each of these substances proved to be more 

 toxic than the other alkaloids with which I experimented. The addi- 

 tion of from | c.c. to 1 c.c. of the digitalin solution to 100 c.c. of 

 sea-water was sufficient to retard cleavage, and to produce various ab- 

 normalities in the segmentation process. (The eggs would divide into 

 two unequal portions, from which other cells are budded off quite 

 irregularly, so that after a time the whole egg is broken up into a mass 

 of small and large fragments, of either round, oval, or triangular 

 shape.) In sea-water with half that amount of digitalin (J c.c. to 

 \ c.c.) cleavage is also retarded, but no abnormalities are to be ob- 

 served. In none of these dilutions of digitalin, however, can develop- 

 ment proceed very far, rarely beyond the gastrula stage. But in still 

 more dilute concentrations of digitalin, as when only one or two drops 

 of the standard solution is added to 100 c.c. of the sea-water, the eggs 

 develop more or less normally, differing with different lots of eggs, 

 and reach the pluteus stage. But the plutei are as a rule smaller than 

 those developed in pure sea-water. In Table VI are combined the data 

 from two separate experiments to illustrate the above statement. 



Quinine is likewise very injurious to the developing eggs in concen- 

 trations ranging from 1 c.c. to 2 c.c. of the standard solution in 100 c.c. 

 of sea-water. The effect is shown in a retardation of the segmenta- 

 tion process, which is greater the stronger the solution. But when 

 much smaller quantities of the quinine solution (\ c.c. to | c.c.) are 

 diluted in 100 c.c. of sea-water, the segmentation of the eggs is normal 

 and unchecked. In none of the solutions do the eggs develop very 

 far, but the stage reached in the various solutions is inversely propor- 

 tional to the concentration ; while in a concentration 1 : 80000 (i c.c. 

 to 100 c.c. of sea-water) the eggs may develop up to the gastrula stage, 

 they probably never go beyond the 8-cell stage in a concentration 

 1 : 10000. Table VII reproduces the record of one of the experiments. 



Unfortunately, lack of time did not permit me to complete the 

 experiments with quinine and to determine the limit of toxicity of 

 this alkaloid and its effect upon the size of the developing larvae. It 

 does not seem to me improbable, however, that, as in the previous 

 experiments, the size of embryos would have been reduced in quinine 

 solutions in which their development was possible. 



